The present invention relates to a compressor system for compressing gases in a multistage compression and a method for operating a compressor system.
A previously known compressor system for achieving a multistage compression comprises multiple compressors connected in series, specifically an upstream compressor and a last compressor, which defines the highest compressor stage within the multistage compression, one or more intercoolers between upstream compressor and last compressor, and an adsorption dryer, which is connected downstream of the last compressor and which is designed as a rotation dryer and comprises a regeneration sector and a drying sector, wherein the regeneration sector is connected to the last compressor in such a manner that the gas stream output from the last compressor is guided completely in the full stream principle through the regeneration sector of the adsorption dryer.
Such multistage compressor systems or multistage compression methods are known per se, in which, at the last compressor, which defines the highest compressor stage within the multistage compression, an adsorption dryer, which is designed as a rotation dryer and comprises a regeneration sector and a drying sector, wherein the regeneration sector is connected to the last compressor in such a manner that the gas stream output from the last compressor is guided completely in the full stream principle through the regeneration sector of the adsorption dryer.
However, one problem is that a compressed and dried gas stream is to be available at the outlet of the drying sector, which has to be sufficiently dry with respect to an established limiting value. In general, the pressure dewpoint is used as the measure of the dryness of the dried gas and thus for the drying result of the drying process. The pressure dewpoint specifies the temperature to which a compressed gas stream may be maximally cooled, without water vapor contained therein precipitating as condensate or ice. In the drying process provided here, the gas stream exiting from the last compressor is guided completely through the regeneration sector of the adsorption dryer designed as a rotation dryer, so that the compression heat, which occurs in any case, may be used efficiently for desorption of the water previously adsorbed in the adsorption material of the rotation dryer. The adsorption material, which is thus regenerated as extensively as possible in the regeneration sector, is used again in the drying sector for the gas drying after the regeneration.
To be able to ensure sufficient drying, i.e., maintaining a fixed limiting value for the pressure dewpoint, compressed gas of sufficiently high temperature has to be applied to the regeneration sector by the last compressor. The temperature at which the compressed gas exits from the last compressor and enters the regeneration sector is referred to hereafter as the regeneration entry temperature TRi and, as mentioned, has to be sufficiently high. For the purposes of the following application, the exit temperature from the last compressor TAl is assumed to be equal to the regeneration entry temperature TRi (TAl=TRi). Even if the compressed gas should cool down slightly between the outlet from the last compressor and the inlet into the regeneration sector, this may thus be neglected in most practical systems. In any case, however, it is to be noted that the regeneration entry temperature TRi is directly correlated with the exit temperature from the last compressor TAl.
If the regeneration entry temperature TRi is excessively high, this may be linked to various disadvantages. On the one hand, the hazard exists that excessively high temperatures will be applied to downstream components in a connected compressed air system, for which they are not designed, i.e., the permissible operating temperatures of components connected downstream will be exceeded.
On the other hand, an excessively high regeneration entry temperature TRi is also correlated with a correspondingly higher entry temperature of the gas into the last compressor. The compression of a hotter gas is significantly more inefficient, however, than the compression of a comparatively cooler gas, with the result that the compression process becomes inefficient.
Since boundary conditions, for example, the temperature of coolant media, which are available for cooling of the intercooler or intercoolers, or also the speed and therefore the power of one or more compressors may change under specific operating conditions, the regeneration entry temperature TRi may therefore firstly also change in its value.
It has thus already been proposed in the prior art, to maintain a specified degree of drying of a compressed gas, to regulate the regeneration entry temperature TRi to an established value. Such a solution is described, for example, in JP-S56152726. Specifically, a two-stage compression comprising an upstream compressor and a last compressor is proposed therein, wherein an intercooler is provided between the upstream compressor and the last compressor. A regulated cooling water stream is applied to the intercooler provided therein such that the exit temperature of the compressed gas from the last compressor and therefore the regeneration entry temperature TRi is always kept above a set minimum temperature. Drying is caused in the prior art by a switched dryer to be regenerated in phases. The regeneration of the adsorption dryer, which is designed therein as a switched dryer, is always carried out at at least the established minimum temperature due to the regulation of the cooling water stream applied to the intercooler.
Proceeding from this prior art, an object of the present invention is to propose a compressor system or a method for operating a compressor system, in which the overall energy efficiency is improved in a multistage compression having subsequent adsorption drying of the compressed gas.